Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Actuarial changes, tax	$ 174	$ 47	$ (151)
Prior service cost, tax	(19)	203	2
Other, tax	$ 0	$ 0	$ 0

Amount of tax (expense) benefit, after reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to net prior service cost (credit) pension and other postretirement defined benefit plans.

No definition available.

Name:	mpc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansNetPriorServiceCostCreditAdjustmentTax
Namespace Prefix:	mpc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration